Mitt Romney's presidential campaign said Monday it was pulling a television ad hitting rival Rick Santorum while Santorum tends to his young daughter Isabella, who was admitted to a hospital Friday.

The sharply negative ad, which was to begin airing in the April 24 primary battleground state of Pennsylvania, highlighted Santorum's 2006 reelection loss in the state.

Romney campaign spokeswoman Andrea Saul said the decision was made "out of deference to Sen. Santorum's decision to suspend his campaign for personal family reasons."

Despite Saul's use of the word "suspend," Santorum has not formally suspended his campaign and is scheduled to resume campaigning Tuesday.

Santorum, Romney's closest rival in the delegate count, announced Friday that he was canceling Monday campaign events after his daughter, whom the family calls Bella, was hospitalized for the second time this year. Bella suffers from a chromosomal condition called Trisomy 18.

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Santorum spokesman Hogan Gidley told CNN that the Santorum family expects Bella to be released from the hospital later Monday.

"We appreciate the outpouring of support and prayers," Gidley told CNN. "The prayers worked, she's doing much better, so we're thankful for that. It puts things in perspective."

Santorum and former House Speaker Newt Gingrich have resisted calls to end their races in the face of Romney's substantial lead in the delegate count.

On Sunday, Gingrich admitted that Romney was the "likely" nominee.

"I think you have to be realistic," Gingrich said on "Fox News Sunday." "Given the size of his organization, given the number of primaries he's won, he is far and away the most likely Republican nominee."

CNN's latest estimate shows the GOP delegate tally at Romney with 659, Santorum with 275, Gingrich with 140 and Rep. Ron Paul with 71; 1,144 delegates are needed to clinch the nomination.

In addition to Pennsylvania, New York, Connecticut, Rhode Island and Delaware also vote on April 24. In all, 231 delegates are up for grabs in the five states.

Asked last week if Santorum would win in his home state, Romney said, "I think everybody expects someone to win their home state. Newt Gingrich won his state. I won my state. I think people expect the senator to win his home state.

"But I hope to pick up a lot of delegates, and we have several other states in the contest on the same day. I would like to win all of those, and if I can win the others and pick up some delegates here, it would give me a stronger lead."

Asked Sunday if Santorum should get out of the race, Gingrich said, "No, I think he has to make that decision."

The former House speaker has said he will stay in the race until the Republican National Convention in August, despite running a distant third in the delegate count.

The long campaign and the punches and counterpunches from Gingrich and Santorum have taken their toll on the presumed nominee, especially among independent voters, according to a recent USAToday/Gallup poll of independents in swing states.

"I think Romney through the primaries has been beaten up by the others, seen as removed from, kind of, the middle-class, average voter. Has trouble with women now, with Latinos," Democratic strategist and pollster Mark Penn said on CNN's "State of the Union" on Sunday.

"Boy, I think he's entering the general election now kind of -- a totally beaten-up candidate, and this poll is a reflection of that."

But Republican pollster and strategist Linda Divall said that's normal in a campaign and there's time to repair the damage.

"Number one, it's early April. Number two, when you look at it with registered voters, the margin becomes much closer. Thirdly, this is not atypical in a very competitive Republican primary, that our nominee tends to go down," she told "State of the Union" anchor Candy Crowley.

"The other thing that's stymieing Mitt Romney somewhat is the perception of the Republican Party, which has also suffered a little bit of a beating," she said.

"So, I think as the Romney campaign is able to regroup, bring in their general election team and strike some very clear themes between himself and the president, which they started to do with the speeches the last few days ... you'll see a pretty stark contrast in terms of what is the direction that this country should be pursuing -- in terms of the economy and jobs and getting the deficit under control."

In all but conceding the GOP race, Gingrich said he won't give up on trying to influence the party's platform that emerges going into the general election.

"I think platforms matter in the long run in the evolution of the party. And the party is more than just a presidential candidate -- it's Senate candidates, House candidates, state legislators," he said.

Gingrich said Sunday that he thinks Romney will adopt some of the positions that he's advocated: energy independence, personal Social Security accounts, keeping the government from trying to impose itself on religious values and paying down the debt. He said revenue from expanding domestic energy should be directed toward that.

And Gingrich said he has already talked to Republican National Committee Chairman Reince Priebus about working in the fall "to help defeat Obama any way I could -- whatever the team thinks I can do to be helpful, I would do."

Beyond that, he said he wouldn't want to serve in a Romney administration and would rather "go back to a post-political career."